Colonization of old-forest lichens in a young and an old boreal Picea abies forest: an experimental approach Original Research Article

Understanding the factors limiting the distribution of a species is crucial for designing conservation strategies. We evaluated whether the scarcity of old-forest lichens in young forests was due to unfavourable environmental conditions for colonization in young stands or to dispersal limitations. Vegetative diaspores of Lobaria scrobiculata, Platismatia glauca and Platismatia norvegica were sown on 240 spruce twigs transplanted to a young and an old stand of spruce. Our results demonstrate that the old-forest species established and grew as rapidly in the young as in the old forest. Higher light levels in the young, compared with the old forest, did not reduce diaspore development. Moreover, greater numbers of juvenile thalli of Platismatia were found on control twigs (unsown) in the old forest, compared with the young forest, suggesting higher propagule density and more efficient dispersal in the old stand. Our results indicate that life-history characteristics, which include dispersal characters, are important for explaining the species scarcity in younger stands. Minimizing the distance between regeneration units and potential sources of propagules is probably important for maintaining lichen biodiversity in managed forest ecosystems.